diff --git a/application/models/item_quantities.php b/application/models/item_quantities.php
index 1ec21a184..0094fd32e 100644
--- a/application/models/item_quantities.php
+++ b/application/models/item_quantities.php
@@ -47,5 +47,20 @@ class Item_quantities extends CI_Model
         }          
         return $result;   
     }
+	
+	/*
+	 * changes to quantity of an item according to the given amount.
+	 * if $quantity_change is negative, it will be subtracted,
+	 * if it is positive, it will be added to the current quantity
+	 */
+	function change_quantity($item_id, $location_id, $quantity_change)
+	{
+		$quantity_old = $this->get_item_quantity($item_id, $location_id);
+		$quantity_new = $quantity_old->quantity + intval($quantity_change);
+		$location_detail = array('item_id'=>$item_id,
+									'location_id'=>$location_id,
+									'quantity'=>$quantity_new);
+		return $this->save($location_detail,$item_id,$location_id);
+	}
 }
 ?>
\ No newline at end of file
diff --git a/application/models/receiving.php b/application/models/receiving.php
index b104b3ec9..62f300ee2 100644
--- a/application/models/receiving.php
+++ b/application/models/receiving.php
@@ -137,11 +137,17 @@ class Receiving extends CI_Model
 						'trans_items'=>$item['item_id'],
 						'trans_user'=>$employee_id,
 						'trans_comment'=>'Deleting sale ' . $receiving_id,
-						'trans_inventory'=>$item['quantity_purchased']
+						'trans_location'=>$item['item_location'],
+						'trans_inventory'=>$item['quantity_purchased']*-1
 	
 				);
 				// update inventory
 				$this->Inventory->insert($inv_data);
+
+				// update quantities
+				$this->Item_quantities->change_quantity($item['item_id'],
+														$item['item_location'],
+														$item['quantity_purchased']*-1);
 			}
 		}
 		// delete all items
diff --git a/application/models/sale.php b/application/models/sale.php
index c13b1a8db..361fd587f 100644
--- a/application/models/sale.php
+++ b/application/models/sale.php
@@ -184,11 +184,17 @@ class Sale extends CI_Model
 						'trans_items'=>$item['item_id'],
 						'trans_user'=>$employee_id,
 						'trans_comment'=>'Deleting sale ' . $sale_id,
-						'trans_inventory'=>$item['quantity_purchased']
+						'trans_location'=>$item['item_location'],
+						'trans_inventory'=>$item['quantity_purchased']*-1
 	
 				);
 				// update inventory
 				$this->Inventory->insert($inv_data);
+
+				// update quantities
+				$this->Item_quantities->change_quantity($item['item_id'],
+														$item['item_location'],
+														$item['quantity_purchased']*-1);
 			}
 		}
 		// delete all items